1. Field of the Invention
The present invention relates to a control method of a gap adjuster of an impact crusher and a gap adjuster. More specifically, it relates to a control method of a gap adjuster and a gap adjuster provided on an impact crusher including a rotor having an impact body, a rebound plate spaced apart from a rotation locus of the tip end of the impact body, and a case for the rotor and the rebound plate to be attached.
2. Description of Related Art
Conventionally, it is known to crush an object such as great mass of concrete and asphalt taken out from demolition site of a building and a quarry and natural stone such as andesite with an impact crusher.
Such impact crusher crushes the object by hitting the object with an impact plate (impact body) of a revolving rotor and by colliding the object hit by the impact body with a rebound plate. At this time, since the size of the object (the size of the object after being crushed) is determined by the gap between the rotation locus of the impact plate and the rebound plate, the gap has to be accurately adjusted and maintained by moving the rebound plate in order to obtain the object of a predetermined size.
For adjusting the gap, in a method disclosed in Japanese Patent Laid-Open Publication No. Hei8-266921, a rebound plate is brought into contact with an impact plate, the contact position being set as a zero-point position of the rebound plate, and the rebound plate is moved back by a predetermined distance with a hydraulic cylinder, thereby automatically adjusting the gap relative to the impact plate.
However, though the rebound plate can be seamlessly and continuously moved when the rebound plate is moved by the hydraulic cylinder as in the above method, it is difficult to minutely move the rebound plate or securely stop at a desired position while moving, so that accurate movement by a desired movement distance cannot be conducted. Accordingly, the gap between the rebound plate and the impact plate cannot be accurately adjusted, and gap accuracy is deteriorated.
Further, according to the above method, when the rebound plate is adjusted to zero-point position, the rebound plate is brought closer to the rotor while rotating the rotor at a high speed before bringing the rebound plate into contact with the impact plate, where the magnitude of vibration of the rebound plate periodically generated by the contact is detected. When the magnitude of the vibration reaches a predetermined vibration limit, the position of the rebound plate is determined as the zero-point position.
However, since the rebound plate is vibrated by the rotation of the rotor while determining the zero-point position, it is vague which position during vibration should be determined as the zero-point position, so that it is difficult to instantly determine accurate zero-point position.
Further, since the magnitude of the vibration of the rebound plate greatly differs according to abrasion of the rebound plate and the impact plate, the zero-point position is shifted on account of the abrasion of the rebound plate and the impact plate when the magnitude of the vibration is always compared with the same vibration limit, so that the zero-point position cannot be accurately determined. Considering the fact that abrasion changes on account of various factors, it is virtually impossible to set the vibration limit in accordance with abrasion.
Accordingly, since the gap is adjusted while determination of the zero-point position is inaccurately conducted, the gap cannot be accurately adjusted.